Hot gas engine with improved gas pressure control



Aug. 5, I969 HOT GAS ENGINE WITH IMPROVED GAS PRESSURE CO NTROL Filed Dec. 19. 1967 F. E. HEFF'NER iv v? t GAS F COMPRESSOR I I r,

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' f7? w 4 4 if CONTROL on. 9? PRESSURE STORAGE TANK I I I W "v6 A w i4 1 A w I I2 i INVENTOR. ifmcfs 5. Hafiz/er w W 5 BY ud% KM ATTORNFV United States Patent US. Cl. 60-24 6 Claims ABSTRACT OF THE DISCLOSURE A hot gas engine includes pressure control means for varying the pressure in a plurality of enclosed gas containing spaces which vary in pressure in an out of phase relationship. The control means provide for filling the spaces from a storage tank without permitting bypassing of gas between the spaces. In addition, reduction of pressure by returning gas to the storage tank is provided with simultaneous bypassing of gas between the spaces to reduce power. Check valves used in the fill lines to prevent bypassing during filling are placed between the fill valves and the storage tank to prevent their being subject to engine pressure variations except during filling.

BACKGROUND OF THE INVENTION This invention relates generally to external combustion hot gas engines and more specifically to improved means for controlling the gas pressure in such an engine.

It is known in the art relating to closed cycle hot gas engines, for example, of the Stirling cycle type, to control the power output of such engines by varying the quantity of gas in the engine working space or spaces, as the case may be. It is also known to provide a storage tank from which gas is supplied to the engine to increase the working gas pressure and to which gas is returned from the engine to reduce the working gas pressure. A compressor may be used to return the gas to the storage tank.

There are many arrangements of hot gas engines which include a power piston reciprocating in a cylinder and having a variable volume working space defined, in part, by one end of the power piston. The other end of the power piston usually defines, in part, a second enclosed space. In single acting engines, this may be a butter space in which gas pressure is utilized to reduce the working gas forces acting on the engine operating mechanism. In double acting engines, the second space is an additional working space imparting power to the power piston. In both types of engines, it is desirable that the average pressures in the two spaces be approximately equal and that variations in the pressures be accomplished by adding gas to or withdrawing gas from both spaces concurrently.

When gas is being withdrawn from the engine to reduce power, the two spaces are often connected through a bypass valve to provide an immediate power reduction while the more gradual reduction in gas pressure is taking place. However, when the engine gas pressure is being increased, the purpose is to increase engine power and it is therefore undesirable to permit bypassing of gas between the spaces at this time.

One gas pressure control arrangement for accomplishing the foregoing purposes is shown in United States patent application Ser. No. 522,553 Brandes, now Patent No. 3,355,881, granted Dec. 5, 1967. In the arrangement disclosed in this patent, the gas storage tank is connected to the engine working and buffer spaces by a single fill valve. A pair of check valves connecting each of the working and buffer spaces with the fill valve are utilized to prevent undesired bypassing of gas between the spaces.

While this arrangement is known to function successfully, it has been found in practice that the durability of the check valves is reduced by the fact that they are constantly exposed to the substantial pressure fluctuations in the working and buffer spaces. This has resulted in early failure and leakage of the valves, giving undesired bypassing of the working gas and a loss of engine etficiency.

SUMMARY OF THE INVENTION The present invention provides an improved arrangement of gas pressure control means for hot gas engines of the type described. In this arrangement, a separate fill valve is utilized for each variable volume space which is to be supplied with gas from the storage tank. The check valves are then located between individual fill valves and the storage tank so as to permit only unidirectional flow through each fill valve from the storage tank to the engine. In this way, the check valves act in the usual manner to prevent bypassing of flow between the variable volume spaces being filled when the fill valves are open. However, during constant pressure operation or load reduction, when the fill valves are closed, the variations in pressure in the variable volume engine spaces are prevented by the closed fill valves from reaching the check valves and thus, the check valves are affected by these pressure variations only during the time when engine gas pressure is being increased. In this way, the durability of the check valves is significantly increased.

These and other advantages of the invention will be more readily understood from the following description of a preferred embodiment of the invention. While the invention is illustrated as applied to the working and buffer spaces of a single acting one cylinder engine, it should be apparent that the arrangement is also applicable to double acting engines as well as to the various working and/or buffer spaces of multiple cylinder englnes.

BRIEF DESCRIPTION OF THE INVENTION FIGURE 1 of the drawings illustrates a hot gas engine having gas pressure control means according to the invention;

FIGURE 2 shows a portion of the gas pressure control means of FIGURE 1 illustrating the actuating means in a position in which the fill valves are open to permit the transfer of gas to the engine working and bulfer spaces and FIGURE 3 shows a portion of the gas pressure control means of FIGURE 1 illustrating the actuating means in a position in which the dump and bypass valves are open to permit the discharge of gas from the engine working and butter spaces.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring more specifically to the drawing, numeral 10 generally indicates an external combustion hot gas engine of the Stirling cycle type and comprising a cylinder 12 in which are coaxially reciprocable a displacer piston 14 and a power piston 16. The pistons are conventionally arranged with the displacer piston rod 18 being received concentrically through the power piston 16 and the power piston rod 20 for connection to a conventional drive mechanism (not shown). The cylinder is closed at its upper and lower ends and is separated into a bulfer space 22 below the power piston and a working space 24 above the power piston. Due to the reciprocating action of the power piston, the working and buffer spaces vary in volume in an out of phase relationship to one another.

The displacer piston 14 reciprocates out of phase with the power piston and completely within the working space in the upper portion of the cylinder dividing it into a hot zone 26 above the displacer piston and a cold zone 28 below the displacer piston. These zones are connected through a conventional heater 30, regenerators 32 and coolers 34 which comprise a part of the working space and through which the engine working gas is alternately cycled between the hot and cold zones by the displacer piston.

The combined action of the power and displacer pistons provides a cycle of operation in the working gas including compression, heating, expansion and cooling phases which result in a network output to the power piston. In order to reduce mechanical loads on the operating mechanism, the buffer space 22 is also filled with compressed gas which varies in pressure in a cycle opposite to that of the gas in the working space.

In order to change the engine power output, means are provided for varying the quantity of gas in the working space. The quantity of gas in the buffer space is varied concurrently therewith in order to keep a proper relationship between the working and buffer pressures.

As illustrated in FIGURE 1, the gas pressure control system includes gas storage means such as storage tank 36, a gas compressor 38 and a control unit 40. The control unit includes a housing 42 having a pair of spring biased fill valves 44 and 46 arranged along one side thereof with a similar appearing pair of valves arranged along the opposite side but acting as a dump valve 48 and a combination dump and bypass valve 50. A pivotally mounted actuating lever 52 is arranged to engage and actuate concurrently either the two fill valves 44, 46 or the two other valves 48, 50. Spring biasing means 54 act against one end of lever 52 and are opposed by a fluid pressure responsive diaphragm actuator 56 to control the position of the lever. A pair of spring biased ball check valves 58 and 60 are also located in the housing as will be subsequently described.

The storage tank, gas compressor and the various valves of control unit 40 are interconnected with the working and buffer spaces of the engine in the following manner, The storage tank 36 is connected with the working space 24 through a line 62 and internal housing passages extending through check valve 58 and fill valve 44 to a line 64 which connects with the engine working space. The storage tank connects with the buffer space 22 through the line 62 and internal housing passages through check valve 60 and fill valve 46 which connects to a line 66 leading to the engine buffer space 22. Check valves 58 and 60 permit only unidirectional fiow through fill valves 44 and 46 so that flow through line 62 may pass only from the storage tank to the engine and not in a reverse direction. The check valves also prevent bypassing of flow between the working and buffer spaces through the fill valves.

The engine working space 24 is connected to the storage tank through another path via line 64 and through internal housing passages extending adjacent bypass valve 50 and through dump valve 48 to a line 68. Line 68 leads to gas compressor 38 which then connects with the storage tank through a line 70. Buffer space 22 is also connected to the storage tank through an alternate path via line 66 and through internal housing passages through bypass valve 50 and dump valve 48 to line 68, gas compressor 38 and line 70. The working and butter spaces are also connected through lines 64 and 66 and internal housing passages extending through bypass valve 50.

In operation, oil pressure generated by a control device (not shown) acts against the diaphragm actuator 56 to position lever 52 in either the neutral position of FIG- URE 1 or positions below or above the neutral position as shown in FIGURES 2 and 3, respectively. When the lever is in the neutral position of FIGURE 1, the fill valves 44 and 46, dump valve 48 and bypass valve 50 are all closed, preventing any transfer of gas between the storage tank and the engine buffer and working spaces and thus holding the quantity of gas in the engine constant except for leakage.

When it is desired to increase engine power, oil pressure on diaphragm actuator 56 is reduced, permitting spring biasing means 54 to move lever 52 downwardly as shOWn in FIGURE 2. This opens fill valves 44 and 46 permitting pressurized gas to pass from the storage tank through the check valves and fill valves to the working and buffer spaces. If the storage tank pressure is below the maximum reached in these spaces during their operating cycle, the flow may be intermittent, but it will be unidirectional since the check valves will prevent any return flow as well as any bypassing between the two spaces. Upon a sufiicient increase in gas pressure in the engine spaces, the control means are returned to the neutral position of FIGURE 1 cutting olf further flow.

When it is desired to decrease engine power, oil pressure on the diaphragm 56 is increased, causing lever 52 to move upwardly as shown in FIGURE 3. This action opens dump valve 48 and bypass valve 50 permitting the bypassing of gas between the working and buffer spaces so as to immediately reduce engine power. Concurrently, gas from both spaces is discharged through dum valve 48 to the gas compressor, which forces the gas through line 70 into the storage tank 36. When a sufiicient pressure reduction has been made, the control device is returned to the neutral position of FIGURE 1, again cutting off further gas flow.

In the neutral position, the cyclic pressures of the working and buffer spaces act solely on the mechanically actuated valves 44, 46, 48, 50 which, due to their construction, are better able to resist these forces without damage to the valves than are the pressure actuated check valves 58, 60. The latter are protected from these damaging pressures due to their positions intermediate the fill valves 44, 46 and the storage tank.

While the invention has been disclosed by reference t a single embodiment showing an engine having a single working space and a single buffer space on opposite sides of the power piston, it should be apparent that the system may equally well be utilized in conjunction with a double acting engine having working spaces on either side of the power piston as well as, with suitable modifications, in multiple cylinder engines of either the single or double acting type. Since other changes within the skill of the art may also be made within the spirit and scope of the invention disclosed herein, it is desired that the invention not be limited except in accordance with the language of the following claims.

I claim:

1. In combination with a hot gas engine having a plurality of gas containing enclosed spaces arranged to cyclically vary in pressure in out of phase relation to one another, gas storage means, means connecting said enclosed spaces with said gas storage means for transferring gas therebetween and control means associated with said connecting means to control the gas pressure in said spaces, said control means comprising a plurality of fill valves in said connecting means, one

intermediate each of said enclosed spaces and said gas storage means and operable to permit the transfer of gas to said spaces,

actuating means adapted to contact said fill valves and operable to open all said valves concurrently, and

a plurality of check valves in said connecting means,

one intermediate each of said fill valves and said gas storage means and arranged to permit flow from said gas storage means to said fill valves but to prevent flow in an opposite direction,

whereby flow through said fill valves is unidirectional and bypassing of gas between said enclosed spaces through said fill valves is prevented.

2. In combination with a hot gas engine having a cylinder, a power piston in said cylinder and, in part, defining at opposite ends of said piston a pair of enclosed variable volume gas containing spaces, gas storage means, means connecting said enclosed spaces with one another and with said gas storage means for transferring gas therebetween and control means associated with said connecting means to control ga transfer therethrough, said control means comprising a pair of fill valves, one intermediate each of said enclosed spaces and said gas storage means and operable to permit the transfer of gas to said spaces, actuating means adapted to contact said fill valves and operable to open both said valves concurrently and a pair of check valves, one intermediate each of said fill valves and said gas storage means and arranged to permit flow from aid gas storage means to said fill valves but to prevent flow in an opposite direction, whereby flow through said fill valves is unidirectional and bypassing of gas between said enclosed spaces through said fill valves is prevented. 3. The combination of claim 2 wherein said enclosed spaces include a working space wherein said gas goes through a heat power cycle by which heat energy input is converted to work output to the power piston and a buffer space wherein pressurized gas, at least in part, balances working ga pressures on the engine power piston. 4. The combination of claim 2 wherein said control means further include a bypass valve intermediate said two enclosed spaces and operable to permit the bypassing of gas around the power piston,

a dump valve intermediate said ga storage means and one of said spaces and operable to permit the flow of gas therebetween and a compressor intermediate said dump valve and said gas storage means and operable to receive gas from said dump valve and deliver it to said storage means,

said actuating means being adapted to contact said dump and bypass valves and operable to open said dump and bypass valves concurrently so as to permit gas flow from both said spaces to said gas storage means concurrent with the bypassing of gas flow around said power piston.

5. The combination of claim 4 wherein said enclosed spaces include a working space wherein said gas goes through a heat power cycle by which heat energy input i converted to work output to the power piston and a buffer space wherein pressurized gas, at least in part, balances working gas pressures on the engine power piston.

6. The combination of claim 5 wherein said dump valve is connected directly with said working space and indirectly with said bufier space through said bypass valve.

References Cited UNITED STATES PATENTS 2,794,315 6/1957 Meijer 24 3,355,881 12/1967 Brandes 6024 3,372,539 3/1968 Reinhoudt 6024 EDGAR W. GEOGHEGAN, Primary Examiner US. Cl. X.R. 626 

